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---
slug: /
id: welcome
title: 👋 Welcome
sidebar_position: 1
---
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Welcome to Fiber's online API documentation, complete with examples to help you start building web applications right away!
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**Fiber ** is an [Express ](https://github.com/expressjs/express )-inspired **web framework ** built on top of [Fasthttp ](https://github.com/valyala/fasthttp ), the **fastest ** HTTP engine for [Go ](https://go.dev/doc/ ). It is designed to facilitate rapid development with **zero memory allocations ** and a strong focus on **performance ** .
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These docs cover **Fiber v3 ** .
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Looking to practice Fiber concepts hands-on? Check out our [Learning Resources ](./extra/learning-resources ) for interactive challenges and tutorials.
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### Installation
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First, [download ](https://go.dev/dl/ ) and install Go. Version `1.25` or higher is required.
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Install Fiber using the [`go get` ](https://pkg.go.dev/cmd/go/#hdr-Add_dependencies_to_current_module_and_install_them ) command:
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``` bash
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go get github.com/gofiber/fiber/v3
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```
### Zero Allocation
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Fiber is optimized for **high performance ** , meaning values returned from **fiber.Ctx ** are **not ** immutable by default and **will ** be reused across requests. As a rule of thumb, you should use context values only within the handler and **must not ** keep any references. Once you return from the handler, any values obtained from the context will be reused in future requests. Here is an example:
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``` go
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func handler ( c fiber . Ctx ) error {
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// Variable is only valid within this handler
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result := c . Params ( "foo" )
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// ...
}
```
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If you need to persist such values outside the handler, make copies of their **underlying buffer ** using the [copy ](https://pkg.go.dev/builtin/#copy ) builtin. Here is an example of persisting a string:
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``` go
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func handler ( c fiber . Ctx ) error {
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// Variable is only valid within this handler
result := c . Params ( "foo" )
// Make a copy
buffer := make ( [ ] byte , len ( result ) )
copy ( buffer , result )
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resultCopy := string ( buffer )
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// Variable is now valid indefinitely
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// ...
}
```
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Fiber provides `GetString` and `GetBytes` methods on the app that detach values when `Immutable` is enabled and the data isn't already read-only. If it's disabled, use `utils.CopyString` and `utils.CopyBytes` to allocate only when necessary.
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``` go
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app . Get ( "/:foo" , func ( c fiber . Ctx ) error {
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// Detach if necessary when Immutable is enabled
result := c . App ( ) . GetString ( c . Params ( "foo" ) )
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// ...
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} )
```
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Alternatively, you can enable the `Immutable` setting. This makes all values returned from the context immutable, allowing you to persist them anywhere. Note that this comes at the cost of performance.
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``` go
app := fiber . New ( fiber . Config {
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Immutable : true ,
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} )
```
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For more information, please refer to [#426 ](https://github.com/gofiber/fiber/issues/426 ), [#185 ](https://github.com/gofiber/fiber/issues/185 ), and [#3012 ](https://github.com/gofiber/fiber/issues/3012 ).
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### Hello, World
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Here is the simplest **Fiber ** application you can create:
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``` go
package main
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import "github.com/gofiber/fiber/v3"
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func main ( ) {
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app := fiber . New ( )
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app . Get ( "/" , func ( c fiber . Ctx ) error {
return c . SendString ( "Hello, World!" )
} )
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app . Listen ( ":3000" )
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}
```
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``` bash
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go run server.go
```
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Browse to `http://localhost:3000` and you should see `Hello, World!` displayed on the page.
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### Basic Routing
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Routing determines how an application responds to a client request at a particular endpoint—a combination of path and HTTP request method (`GET` , `PUT` , `POST` , etc.).
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Each route can have **multiple handler functions ** that are executed when the route is matched.
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Route definitions follow the structure below:
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``` go
// Function signature
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app . Method ( path string , ... func ( fiber . Ctx ) error )
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```
- `app` is an instance of **Fiber **
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- `Method` is an [HTTP request method ](./api/app#route-handlers ): `GET` , `PUT` , `POST` , etc.
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- `path` is a virtual path on the server
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- `func(fiber.Ctx) error` is a callback function containing the [Context ](./api/ctx ) executed when the route is matched
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#### Simple Route
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``` go
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// Respond with "Hello, World!" on root path "/"
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app . Get ( "/" , func ( c fiber . Ctx ) error {
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return c . SendString ( "Hello, World!" )
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} )
```
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#### Parameters
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``` go
// GET http://localhost:8080/hello%20world
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app . Get ( "/:value" , func ( c fiber . Ctx ) error {
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return c . SendString ( "value: " + c . Params ( "value" ) )
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// => Response: "value: hello world"
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} )
```
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#### Optional Parameter
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``` go
// GET http://localhost:3000/john
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app . Get ( "/:name?" , func ( c fiber . Ctx ) error {
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if c . Params ( "name" ) != "" {
return c . SendString ( "Hello " + c . Params ( "name" ) )
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// => Response: "Hello john"
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}
return c . SendString ( "Where is john?" )
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// => Response: "Where is john?"
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} )
```
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#### Wildcards
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``` go
// GET http://localhost:3000/api/user/john
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app . Get ( "/api/*" , func ( c fiber . Ctx ) error {
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return c . SendString ( "API path: " + c . Params ( "*" ) )
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// => Response: "API path: user/john"
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} )
```
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### Static Files
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To serve static files such as **images ** , **CSS ** , and **JavaScript ** files, use the [static middleware ](./middleware/static.md ).
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Use the following code to serve files in a directory named `./public` :
``` go
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package main
import (
"github.com/gofiber/fiber/v3"
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"github.com/gofiber/fiber/v3/middleware/static"
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)
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func main ( ) {
app := fiber . New ( )
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app . Use ( "/" , static . New ( "./public" ) )
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app . Listen ( ":3000" )
}
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```
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Now, you can access the files in the `./public` directory via your browser:
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``` bash
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http://localhost:3000/hello.html
http://localhost:3000/js/jquery.js
http://localhost:3000/css/style.css
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```
